Question

A group of 12 people who have never met are in a classroom. how many handshakes are exchanged if each pair shakes hands exactly once?

Answer 1

Hey!!
Here is your answer..

First person shakes hands with 11 other persons.

Hence, Second person shakes hands with 10 others
(His hands shake with the first person has already been counted above )

Third person shakes hands with 9 others..
And like this so on..

So, number of handshakes exchanged in the classroom is : 1+2+3+4+5+6+7+8+9+10+11 = 66

Therefore total number of handshakes: 132( 66×2).

This is the answer.
I hope it helps you.